The present invention relates to fluid flow control valves that can be used as a check valve or relief valve which are sometimes referred to as non-return valves. These valves are hereinafter collectively referred to as a self-closing valve or valve. The valve is operable at both low and high pressure fluid operation and is adapted for operation at elevated temperatures.
Self-closing valves of the check and relief valve types are well known in the art. Additionally, self-closing valves with metal to metal sealing arrangements for the movable valve element are also known in the art. An example of such a valve can be found in U.S. Pat. No. 5,893,389. The valve disclosed in the '389 patent has two separate sealing areas; one effective for sealing at relatively low pressure and the other seal area being effective for sealing at a relatively high pressure. This particular patent also illustrates some prior art metal seal arrangements.
It is important to provide a good sealing engagement between the movable vale element and the sealing surface or sealing surfaces of the valve seat(s). In the mass production of self-closing valves, such seats require precision machining and assembly so that a part may be used in combination with other parts and still effect good sealing engagement without custom fitting of parts. Such precision fitting of parts is a particular problem when a valve is designed to operate at both high and low pressures utilizing two distinct sealing areas.
There is thus a need for an improved self-closing valve that eliminates one or more deficiencies of the prior art.